Jim at AZ Snakepit complains that the Diamondbacks aren’t getting their due thanks to a poor regular-season run differential:
Ah, yes: the old “the Diamondbacks were just lucky” argument. First, this demonstrates a basic misunderstanding, very common among statheads, about the game of baseball. It’s not about having the highest team batting average. It’s not about posting the best run-differential. The game is decided simply by scoring more runs than your opponent on the day. That is the only measure of “best” which actually means anything, because playoff spots are not awarded on the basis of Pythagorean Projections.
Bingo. Dismissing a team’s …read more

The Arizona Diamondbacks have been getting grief for outperforming their Pythagorean record by 11 games in 2007. Although it’s nice to see that Bill James’ creation has worked its way into the mainstream, it’s amusing (or not) to see the formula itself so poorly understood.
Instead of talking about “should win” and “luck,” we ought to be digging deeper. Perhaps there are reasons for Arizona’s success that aren’t immediately obvious? Wouldn’t be the first time.
In his 1982 Baseball Abstract, James identifies a team that regularly finished with better records than their run differential suggested they should. From 1977 through 1981, the …read more